Manufacture of electric switches

ABSTRACT

The invention concerns a method for assembling reed contact units. In assembling such units, one reed is positively held and the second is magnetically held from the first and is aligned with it while so held. A fusible element is sealed to both reeds, the sealing being completed, and the reeds held positively, after the reeds have been displaced relatively through a distance corresponding to the desired gap between the reeds in the finished contact unit.

United States Patent 3,277,558 10/1966 ShafferJr,

Peter M. Zollman Weybridge, England 81 1,033

Mar. 27, 1969 Dec. 21, 1971 Badalex Limited Inventor Appl. No. Filed Patented Assignee MANUFACTURE OF ELECTRIC SWITCHES 3,550,268 12/1970 Santi 29/622 FOREIGN PATENTS 1,013,913 12/1965 Great Britain 29/622 Primary Examiner-John F. Campbell Assistant Examiner-Robert W. Church AttorneyLawrence E. Laubscher ABSTRACT: The invention concerns a method for assembling reed contact units. In assembling such units, one reed is positively held and the second is magnetically held from the first and is aligned with it while so held. A fusible element is sealed to both reeds, the sealing being completed, and the reeds held positively, after the reeds have been displaced relatively through a distance corresponding to the desired gap between the reeds in the finished contact unit.

G=0 G=g 5:

=h =0 H o PATENTED 05021 I97I SHEET 2 [IF 2 Tel g INVENTOR ATTORNEY This invention relates to the manufacture of electric contact units of the dry reed type. A contact unit of this type comprises two elongated contact members, or reeds, of paramagnetic material disposed approximately in alignment, with ends overlapping but slightly separated. The arrangement of reeds is such that when the reeds are subjected to a magnetic field of sufficient field intensity, the magnetic attraction between the ends of the reeds is sufficient to cause them to be attracted to each other and to make contact, thereby establishing electrical connection between the two reeds. The reeds are usually mounted by being sealed within an enclosure, suitably of glass.

For certain applications, dry reed contact units are required to operate to a most demanding specification; it may be required that the unit shall continue to operate satisfactorily for a very large number of switching operations, or over a long working life. The present invention is concerned with a method of making a dry reed contact unit which is more convenient to carry out than prior methods at present in use, and which produces an improved contact unit construction.

PRIOR ART In the past various methods of assembling reed contact units have been proposed, with the object of holding the reeds, most commonly two in number, in the correct disposition while the glass envelope is sealed to and about them. Such means usually comprises a pair of clamps for the reeds and another clamp or its equivalent for the glass envelope. The reeds, while held, are passed into the glass envelope and the reeds moved by the clamps until they are in correct disposition, and the assembly is sealed.

The ultimate characteristics and performance of the reed contact unit is very largely dependent upon the very small spacing between the reeds and this calls for very accurate positioning of the reeds in the holding clamps and very accurate movement and positioning of the clamps themselves.

THE OBJECT OF THE INVENTION The object of the invention is to provide a method of and means for assembling reed contact units in which more accurate contact positioning and hence improved performance of a contact unit can be obtained, without the need for the increased precision required by the proposals of the prior art.

Another object of the invention is to simplify the construction of the contact holding and positioning means of a reed contact unit assembly machine.

Another object of the invention is to provide a contact unit which by reason of the accuracy of disposition of the contacts, has a long working life.

THE INVENTION With the invention, the two contacts are held magnetically together, one supported by the other, before being held firmly by the holding means. In this way, when gripped by two supporting means the contacts are in the correct disposition and in particular in intimate surface to surface contact. The contacts can then be separated to the desired extent and sealed to the envelope.

Thus, the invention consists of a method of making a magnetic reed contact unit of the type comprising a fusible enclosure and at least two magnetic contact members mounted in said enclosure, which comprises supporting the first contact member from a support means, supporting the second contact member magnetically from the first, passing a double openended enclosure member over said two contact members, sealing the second contact member to said enclosure member while said second contact member is still magnetically supported from the first contact member, releasing the magnetic support of the second contact member from the first, leaving the second contact supported by the enclosure member, moving said enclosure member and support means relatively to produce a desired separation of the two contact members, and

sealing the first contact member to said enclosure member to hold said contact members with the desired separation.

THE DRAWINGS Features and advantages of the invention will also appear from the following description of embodiments thereof, given by way of example, in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic sectional view of a reed contact unit with its operating coil in position;

FIG. 2 is a diagrammatic side elevational view of the contact unit of FIG. ll;

FIGS. 3(a) to 3(g) are diagrams showing the successive stages in the assembly of a reed contact unit such as that shown inFIGS. l and 2;

FIG. 4 is a diagrammatic perspective view, partly broken away, of a semiautomatic assembly machine for assembling reed contact units.

THE DESCRIPTION The reed contact unit shown diagrammatically in FIGS. 1 and 2 comprises an enclosure 10, consisting of a sleeve of glass, in the ends of which are sealed two elongated reeds 11 and 12. These reeds are made of soft magnetic material. The ends Illa and 12a respectively of the reeds are flattened and are arranged to overlap, as shown. Normally, the flattened portions 11a and 12a are slightly separated from one another, but if a magnetic field is produced about the reeds they become magnetically attracted to each other; the reeds are made sufficiently compliant for these portions to come together under the action of the magnetic force, so as to establish electrical connection between reeds Ill and 12. The operating magnetic field can be provided by any suitable means, but frequently the contact unit is surrounded by a coil, such as 13 which when energized will produce the field sufficient to operate the contacts.

For certain applications, it may be required that a reed contact unit of the type described shall operate successively for a very large number of operations, sometimes millions of opera tions, or it may be required that the contact unit shall continue to operate satisfactorily over a number of years, or both. Despite the apparent simplicity of the contact unit, it is made with considerable accuracy, as the separation between the blade ends of the reeds may be only a few thousandths of an inch and the gap between them, when the unit is not operated, may be set to an accuracy of a fraction of a thousandth of an inch. In the method of making a contact unit, such as that shown in FIGS. 1 and 2, about to be described, the contacts can be positioned to a high degree of accuracy, resulting in a contact unit of improved performance.

The nature of the machine adopted for assembling and sealing the reed contact units will depend on whether the machine is fully automatic or semiautomatic. For fully automatic operation, a turret machine can be used, with successive stations at which the turret dwells and at each or some of which one or more of the operations are carried out. In a semiautomatic machine, described in more detail hereinafter, the loading of the parts and the positioning and sealing is effected at one station.

The machine for this purpose may consist conveniently of a turret-type machine, having a series of positions to which the turret is successively indexed. At a loading position, as indicated in FIG. 3(a), reed 12 is positioned in a holder consisting of jaws M. The reed is disposed with the blade portions IZauppennost and the reed is positioned axially, angularly and longitudinally.

The next operation is indicated in FIG. 3(b). At the same station or at a subsequent station to which the turret has been indexed, a second reed 11 is positioned above the reed 12, with the blade portion Ila downmoszt and overlapping the blade portion 12a of reed 12. Means are then provided for establishing a magnetic field at least in the vicinity of the overlapping portions 11a and 12a of the two reeds, the existence of this field being indicated by the caption H=hin FIG. 3(b). The effect of this field is to cause the two blade portions of the reeds to be magnetically attracted, the force of attraction being sufficient to support the upper reed 11 from the lower reed 12. That the two reeds are in contact, with no gap between them, is indicated by the caption G=o in FIG. 3(b).

As a result of location of the two reeds 11 and 12 in this way, the blade portions 1 1a and 12a will be in close contact as described, but there may be lateral displacement of the blade surfaces, in the manner indicated diagrammatically in FIG. 3(c). FIG. 3(c) indicates the next stage of the process, which may take place at a further station of the turret of the machine, where the two blades are adjusted so that as far as possible the vertical edges of the blade portions are aligned, ensuring that the maximum area of the blades will be in contact with each other. With this object, at the station corresponding to FIG. 3(c) two laterally reciprocating and radially withdrawable fingers 15 and 16 are brought into engagement with the reeds. The fingers have lower portions 15a and 16a respectively which are arranged to pat the sides of the blade portions 11a and 12a and to align them; the fingers l and 16 have upper portions 15b and 16b which engage the upper part of the reed 11, so as partly to support it in the adjusting operation and to ensure that it is in substantial alignment with reed 12. This adjustment of the upper blade is car ried out while the magnetic field is applied, as indicated by the caption H=h in FIG. 3(0); when the fingers 15 and 16 are withdrawn outwardly, the upper reed 1 1 will remain in its now newly adjusted position.

Next, as shown in FIG. 3(d) a short glass tube 17, held in a transfer means (not shown), is threaded downwardly over the upper end of reed 11, until it surrounds the overlapping portions of the reeds and is gripped there by clamping jaws 18; again, this can be carried out at a succeeding position of the turret. In FIG. 3(a) 3(b), and 3(c) the jaws 18 are shown in broken lines, indicating that in these turret positions the jaws are not functioning.

Without variations of the dispositon of the reeds or the glass sleeve 17, in the next operation, indicated in FIG. 3(e) the upper end of the glass tube is sealed, as at 20, while the two reeds 11 and 12 are held in continuing contact by the presence of the magnetic field. The sealing of reed 11 in the sleeve is effected without any relative movement of the two reeds 11 and 12.

While the sleeve 17 continues to be held by jaws 18, the magnetic field is removed; the upper reed 11 will continue to be supported by the glass sleeve. The lower jaws 14, which support the reed 12 are now moved laterally, as indicated by arrow 21, through a distance which corresponds to the separation which it is desired should exist between the blade portions of the reeds 11 and 12 when the contact unit is in its nonoperated condition. This separation is indicated by the caption G=g in FIG. 30).

Finally, the lower end of sleeve 17 is sealed to reed 12, at 22. The sealing may have commenced before or during relative movement of reeds 11 and 12, and the relative movement may occur while the enclosure is in a partially fused and plastic condition. After the cooling of the glass seals, the two reeds 11 and 12 are in the desired operating position.

The lateral alignment of the reed blades, which is effected at the station indicated in FIG. 3(a), proves to be of considerable importance in improving the performance of the contact unit produced on the machine. Because of the exacting requirements of the finished units, there is a certain rate of rejection, and this rate is substantially reduced when the contacts are aligned in the manner described. The mechanical means adopted for this purpose, consisting of the fingers l5 and 16, are very simple and efficacious, and by inserting the sleeve 17 over the reeds after they have been aligned in this way the desired result is obtained without complication of the machine motions. Other methods of aligning the contacts can, however, be adopted.

It is to be observed that the only motions required in the machine, of the highest precision, is that of the lateral movement of the jaws 14, in a direction of arrow 21. No high accuracy movement of any holding means for the upper reed 11 is required, as is the case with certain types of conventional machines for making reed contact units of this general type. Also, the absence of upper holding jaws for the reed 11 again reduces the complexity of the machine. It is to be understood that FIGS. 3(a) to 3(g) may each indicate one or more than one station of the machine.

It may be required that the enclosure 10 of the unit be filled with an inert gas, or gas at reduced pressure. In this case, at least the sealing operations will be carried out in an enclosure filled with the appropriate gas; sealing can be effected either in this arrangement or in the arrangement described, by means of a highly concentrated infrared beam. The infrared source may be located outside the gas enclosure, and directed through a transparent window. The embodiment described is advantageous in this case inasmuch as it requires a minimum of holding devices above the glass sleeve 17, simplifying the construction of the gas enclosure.

The sealing of the lower portion of the glass sleeve 17, at 22 is described above as having been made after a predetermined lateral displacement of the lower jaws 14, to give the desired gap separation of the blades, but if desired this sealing can be carried out with the aid of monitoring means which, for example, may impose a standard intensity magnetic field about the reeds while they are being sealed.

A practical form of semiautomatic assembly machine is shown in a diagrammatic perspective view in FIG. 4. This machine comprises a main supporting framework 30 of metal, having a lower table 31 and an upper table 32. Journalled in bearings carried by the two tables is a vertical drive shaft 33, which is rotated at a relatively slow speed by means of an electric motor 34, a reduction gear unit drive 35 and a drive belt 36, passing round a pulley 37 driven by unit 35 and pulley 38 on shaft 33. The drive shaft 33 carries and drives a series of cams including a cam cylinder 39, and disk cams 40, 41 and 42. The cam cylinder 39 has in its surface a multitum cam groove 43.

A vertically reciprocable shaft 44 is mounted at its lower end in a bearing bush 45, the shaft passing through the upper table 32. The shaft 44 can be reciprocated vertically by a cam follower pin 46 that passes transversely through the shaft 44, and enters the cam groove 43. The pin can move along its own length, transversely through the shaft so that it can enter the groove 43, but can be withdrawn in the opposite direction sufficiently to free the pin from the groove.

Initially, shaft 44 is in a position where the pin 46 is adjacent the lowermost part of the groove 43. The pin is caused to enter the groove and, as the cam cylinder 39 rotates, the pin, in engagement with the groove, causes the shaft 44 to be vertically raised through a cycle of movements. When the pin 46 has been lifted to the uppermost turn of groove 43, it is caused to be withdrawn by a supplementary cam 48 on the end of cylinder 39, whereupon the shaft, no longer supported by the engagement of the pin in the cam groove, drops to the lowermost and initial position. In doing so, the rear end of pin 46 engages a fixed cam 49 by which the pin is caused to move along its own length, again to enter the lowermost part of groove 39; the cycle of movement is then repeated. The fall of the shaft 44 under gravity may be checked by a dashpot 50 at the lower end of the shaft.

As the shaft 44 moves vertically it moves the pivot point of an actuating lever 52; the vertical position of this lever determines which of certain operations will take place when the lever is rotated. The lever is carried on a pivot block 53 which can slide vertically on guide rods 54 and 55 which are mounted, by means not shown, with respect to table 32. The pivot block is attached to an actuating rod 56 the lower end of which is supported from the shaft 44 by means of a support web 57.

The pivotal movement of lever 52 is effected by a push plate assembly, under the control of cams 41 and 42. A plate 60 depending from the underside of table 32 carries a bracket 61 in which are fixed two guide sleeves 62 and 63. Push rods 64 and 65 are guided by the sleeves, the push rods carrying at their one ends push plates 66, 67. A pivoted cam follower 68, operating on cam 40, is connected to push rod 65 through a coupling link 69, and a similar cam follower 70, operating on cam 411, is coupled by link 71 to push rod 64.

As thus far described, when shaft 44 moves vertically moving with it rod 56, block 53 and lever 52, at certain times an actuating roller 72 on the lower end of lever 52 will be opposite one or other of the push plates, and at these times the push plates are moved by the corresponding cam 40 or 41.

The upper end of lever 52 at these predetermined times operates one of a series of actuating slides forming part of a slide assembly for operating this slide assembly which controls the operation shown in FIG. 3.

I claim:

1. A method of making a magnetic reed contact unit of the type comprising a fusible enclosure and at least two generally similar magnetic contact members mounted in said enclosure and having end surfaces which engage when the two contact members are magnetically held which includes supporting a first contact member from a support, moving a second contact member into a position wherein one end surface thereof overlaps an end surface of said first contact member, supporting the second contact member magnetically from the first contact member at the overlap, engaging the edges of said contact members and moving said contact members into alignment at the overlap against the friction caused by magnetic attraction, passing an open-ended enclosure member over the aligned and overlapped contact members while said second contact member is magnetically supported from said first contact member, sealing the second contact member to said enclosure member while said second contact member is still magnetically supported from the first contact member, releasing the magnetic support of the second contact member from the first contact member leaving the second contact member supported by the enclosure member, moving said enclosure member and support means relatively to produce a desired separation of the two contact members, and sealing the first contact member to said enclosure member to hold said contact members with the desired separation.

2. A method in accordance with claim 11 wherein said support means and enclosure are moved relatively while the enclosure is in a partially fused and plastic condition.

3. A method in accordance with claim 1 wherein said adjustment of the flat contact surfaces of the contact members is a lateral adjustment to bring said fiat surfaces substantially into alignment whereby the central longitudinal axes of said contact members are substantially parallel.

4. A method in accordance with claim 3 wherein said second contact member is supported from a second support means and which includes moving said second support means to bring the end portion of said second contact member into overlapping relationship but spaced from the end portion of said first contact member. Said second contact member being positioned above said first contact member, magnetically moving said second contact member into engagement with said first contact member, and releasing said second contact member from said second support means while subsequently magnetically supporting said second contact member from said first contact member.

5. A method in accordance with claim 4, wherein said mag netic support of the second contact member from said first contact member is accomplished by establishing a magnetic field from an external source in the vicinity of said overlapping end portions, said magnetic field being of sufficient strength to draw said end portions together and permit said second contact member to be supported solely by said first contact member. 

1. A method of making a magnetic reed contact unit of the type comprising a fusible enclosure and at least two generally similar magnetic contact members mounted in said enclosure and having end surfaces which engage when the two contact members are magnetically held which includes supporting a first contact member from a support, moving a second contact member into a position wherein one end surface thereof overlaps an end surface of said first contact member, supporting the second contact member magnetically from the first contact member at the overlap, engaging the edges of said contact members and moving said contact members into alignment at the overlap against the friction caused by magnetic attraction, passing an open-ended enclosure member over the aligned and overlapped contact members while said second contact member is magnetically supported from said first contact member, sealing the second contact member to said enclosure member while said second contact member is still magnetically supported from the first contact member, releasing the magnetic support of the second contact member from the first contact member leaving the second contact member supported by the enclosure member, moving said enclosure member and support means relatively to produce a desired separation of the two contact members, and sealing the first contact member to said enclosure member to hold said contact members with the desired separation.
 2. A method in accordance with claim 1 wherein said support means and enclosure are moved relatively while the enclosUre is in a partially fused and plastic condition.
 3. A method in accordance with claim 1 wherein said adjustment of the flat contact surfaces of the contact members is a lateral adjustment to bring said flat surfaces substantially into alignment whereby the central longitudinal axes of said contact members are substantially parallel.
 4. A method in accordance with claim 3 wherein said second contact member is supported from a second support means and which includes moving said second support means to bring the end portion of said second contact member into overlapping relationship but spaced from the end portion of said first contact member. Said second contact member being positioned above said first contact member, magnetically moving said second contact member into engagement with said first contact member, and releasing said second contact member from said second support means while subsequently magnetically supporting said second contact member from said first contact member.
 5. A method in accordance with claim 4, wherein said magnetic support of the second contact member from said first contact member is accomplished by establishing a magnetic field from an external source in the vicinity of said overlapping end portions, said magnetic field being of sufficient strength to draw said end portions together and permit said second contact member to be supported solely by said first contact member. 